// 异步加载城市数据并添加标记点
            fetch('./data/cities.json')
                .then(res => res.json())
                .then(cities => {
                    cities.forEach(city => {
                        viewer.entities.add({
                            name: city.name,
                            position: Cesium.Cartesian3.fromDegrees(city.lon, city.lat),
                            description: city.description,
                            point: {
                                pixelSize: 10,
                                color: Cesium.Color.YELLOW,
                                outlineColor: Cesium.Color.BLACK,
                                outlineWidth: 2,
                                height: 0
                            },
                            label: {
                                text: city.name,
                                font: '14pt sans-serif',
                                pixelOffset: new Cesium.Cartesian2(0, -40),
                                fillColor: Cesium.Color.WHITE,
                                outlineColor: Cesium.Color.BLACK,
                                outlineWidth: 2,
                                style: Cesium.LabelStyle.FILL_AND_OUTLINE
                            }
                        });
                    });
                })
                .catch(err => {
                    console.error('城市数据加载失败:', err);
                });